TPA3255 - all about DIY, Discussion, Design etc

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strongbow60

Member
Joined 2017
chermann said:
i learned that if you use 8 ohm speakers the lrs 350-48 is too weak to push an 8 ohms speaker, because of the max current which you can get --> if you need a lot of power you need...read the thread above...some nice hints from some experts.


for home use ...for me.....its ok
Click to expand...


I'm in no way picking on you chermann, but this "300W is to weak" meme that's floating around here is daft.

To weak for what? To weak for two channels max output in a simulation - yes.

To weak for playing two channels 1 kHz sine wave max output in a resistive load - yes.
To play two channel music at ear-splitting levels, no way!
 
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earsofgold

Member
Joined 2018
strongbow60 said:
I'm in no way picking on you chermann, but this "300W is to weak" meme that's floating around here is daft.

To weak for what? To weak for two channels max output in a simulation - yes.

To weak for playing two channels 1 kHz sine wave max output in a resistive load - yes.
To play two channel music at ear-splitting levels, no way!
Click to expand...

I agree.

It's crazy to me that 300W would not be enough power for someone listening in a living room. :yikes:
 
L

Lo_Tse

Member
Joined 2006
chermann said:
i learned that if you use 8 ohm speakers the lrs 350-48 is too weak to push an 8 ohms speaker, because of the max current which you can get --> if you need a lot of power you need...read the thread above...some nice hints from some experts.


for home use ...for me.....its ok
Click to expand...

Just curious about our comment " ....the lrs 350-48 is too weak to push an 8 ohms speaker...". Was this your personal experience, or you read it somewhere. I think the impedance is less important as compare to the sensitivity when it comes to high sound pressure level.

I have used the 3255 with the lrs 350-48 to drive two pairs of floor standing speakers. Both have a nominal impedance of 8 ohm. One has a sensitivity of 87 db, the other 84 db (pretty insensitive). I can rock the house easily with either pair of speaker, even the low sensitivity one. In addition, quite a few people have reported that even playing loud (using a 3255) for a long period of time, the cooling fan in the lrs 350-48 did not turn on because the PSU never really got hot. I have verified that myself - the lrs 350-48 barely got warm even when I cranked the amp up and played for a relatively long time.

In my personal experience, the lrs 350-48 does not have any problem supplying the power needed by the 3255 to drive a 8 ohm speaker to loud sound level.

Regards,
 
C

chermann

Member
Joined 2017
Hi guys

sorry to intepret my thinking to this expert thread: (in my mind is still my 4 ohms Speakers..)

here is the first AHa effect for me:
https://www.diyaudio.com/forums/class-d/87913-class-amp-photo-gallery-132.html#post5405118

thanks ivx

read on

here i start to check the PSU and i got some nice Information about power.
https://www.diyaudio.com/forums/class-d/309813-wrong-tpa3255-33.html#post5526721


the lrs-350-48 has an maximum current of 7,3Amps for both channels ! =
3,65 Amperes per channel => I^2 *R = 3,65 ^2 * 8 = 106Watt
its enough for listening at home but with speakers lower 86 db and a big room just nice ;)
my lessons learnt is that the LRS is stable but at lower impedances the hick up is starting.

so you do not have 350 WATT i real.

chris
 
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earsofgold

Member
Joined 2018
chermann said:
Hi guys

sorry to intepret my thinking to this expert thread: (in my mind is still my 4 ohms Speakers..)

here is the first AHa effect for me:
https://www.diyaudio.com/forums/class-d/87913-class-amp-photo-gallery-132.html#post5405118

thanks ivx

read on

here i start to check the PSU and i got some nice Information about power.
https://www.diyaudio.com/forums/class-d/309813-wrong-tpa3255-33.html#post5526721


the lrs-350-48 has an maximum current of 7,3Amps for both channels ! =
3,65 Amperes per channel => I^2 *R = 3,65 ^2 * 8 = 106Watt
its enough for listening at home but with speakers lower 86 db and a big room just nice ;)
my lessons learnt is that the LRS is stable but at lower impedances the hick up is starting.

so you do not have 350 WATT i real.

chris
Click to expand...

I don't think it works like that.

Imagine you only have one speaker. By your logic that one speaker would use 7.3^2*8=426W!! Impossible with a 350W PSU.

I don't know how it works, but I don't think it's like that. :)
 
T

Think

Banned
Joined 2017
IVX said:
depends on the speakers, mine is 92dm*m/w and 100W is crazy loud power to me but for 84db*m/w it is not enough for sure. Double power is only +3db in SPL, hence "deaf" 84db*m/w speakers need 630W to get the same SPL as 92db speakers produce at 100W.
Click to expand...
+1
And don't forget power compression, it probably will be over 1000W for the 84dB/W speaker.

Great article: PA Systems
"1 - The Myth of Power Handling Let's look at a simple example. Two systems are set up side-by-side. One has an overall sensitivity of 100dB/W/m, meaning that an input of 1W will give an SPL (sound pressure level) of 100dB at 1 metre distance. Power rating is 100W maximum continuous average for this first example.
The second system is rated at 90dB/W/m sensitivity, but has a power rating of 1,000W - also continuous average. The question is ... which will be louder?"
 
IVX

IVX

Member
Joined 2003
e1dashz.wixsite.com/index
Great article: PA Systems
Click to expand...
Ohh, PA world isn't honest at all, they pretend sale "8ohm drivers" with actual Rdc around 2ohm. How else to report annually about the progress if no new ideas, no new materials? Only cheating with so-called "1W" sensitivity, which actually a voltage 2.828VRMS at 2ohm )) Worldwide more and more popular modus operandi is a lie, I really worry about the future of that planet.
 
2

29285

Disabled Account
Joined 2010
earsofgold said:
I've got a question, if tpa3255 has >65dB PSRR, and meanwell lrs-350-48 has 200mV ripple and noise, how do I calculate how much ripple will show up on the output?
Click to expand...
There is not much you can calculate, because
-PSSR is specified normally at 1khz. It may degrade towards higher frequencies
-ripple is measured with an oscilloscope with a bandwith that far exceeds the audio band.
The ripple content normally is above the audio frequency band.



So this is no information useful to calculate the audible contribution of smps ripple to your audio output.
 
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larzman

Member
Joined 2006
home.comcast.net/~larzman/
jimk04 said:
Looks a cheap way into 10A. Lower ripple and noise than the other usual form factors usually mentioned here.

Not sure if it needs the relay signal switched to operate it.
Click to expand...

No relay switching necessary. The Meanwell power supply simply provides the relay to connect to an external LED or whatever as a DC power status check ok. Worst thing about this PS is the DIN rail mount. I have it mounted on it's side in a very well ventilated metal chassis that also mounts the TPA3255EVM. Pretty good setup in a 2U rack mount chassis that has plenty of room for other small items like a USB jack to power a streaming audio source.

So far, everything sounds good, and it can get quite loud, though I can't max it out as my speakers are rated at 250W.
 
J

JMF11

Member
Joined 2013
I have a question. Is it possible with the TPA3251 (and others in the same chip familly) to adjust the gain, in order to reduce it ? The intention would be to build a sort of power buffer to be plugged after different input stage to do some experiment, in the spirit of M2X – diyAudio Store.


Or of the pass B1 Korg triode (or pMillet equivalent) preamp. The gain of the B1 Korg triode preamp is 17dB. So the gain of the power stage should be lowered.


Is it possible ? Would Sound Quality be lost in the process ?


Best regards,


JMF
 
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